<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>01_伸缩模型_伸缩项目</title>
  <style>
    .outer{
      width: 600px;
      height: 600px;
      background-color: gray;
      display: flex;
    }
    .inner{
      width: 200px;
      height: 200px;
      border: 1px black solid;
      background-color: skyblue;
      /* 设置将边框的尺寸也加入盒子尺寸 */
      box-sizing: border-box;
    }
    .inner3{
      display: flex;
    }
  </style>
</head>
<body>
  <div class="outer">
    <div class="inner">1</div>
    <div class="inner">2</div>
    <div class="inner inner3">
      <div>a</div>
      <div>b</div>
      <div>c</div>
    </div>


  </div>
  
</body>
</html>